The phytochrome A-specific signaling intermediate SPA1 interacts directly with COP1, a constitutive repressor of light signaling in Arabidopsis.
The phytochrome A-specific signaling intermediate SPA1 interacts directly with COP1, a constitutive repressor of light signaling in Arabidopsis.
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DOI：
10.1074/jbc.m103140200
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发表时间：
2001-10
期刊：
影响因子：
--
通讯作者：
U. Hoecker;P. Quail
中科院分区：
文献类型：
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作者：
U. Hoecker;P. Quail
SPA1是一种光敏色素a （phyA）特异性信号介质，在拟南芥幼苗中作为光形态发生的光依赖性抑制因子。它包含一个与光信号组成抑制因子COP1的WD-repeat区域序列高度相似的WD-repeat结构域。通过酵母双杂交和体外相互作用实验，我们发现SPA1与COP1有很强的选择性结合。结构域映射研究表明，SPA1的螺旋状结构域对于与COP1结合是必要和充分的。相反，对COP1蛋白的类似缺失分析表明，SPA1与COP1的螺旋结构域相互作用。为了进一步研究SPA1在phyA信号通路中的功能，我们测试了SPA1是否像COP1一样，在光响应中介导基因表达的变化。我们发现spa1突变在光处理2小时内增加了某些光调节基因的光响应性。综上所述，结果表明SPA1可能将光信号通路中光敏色素a特异性分支与COP1连接起来。因此，我们的数据为COP1是单个光感受器上游信号通路的汇聚点的假设提供了分子支持。
SPA1 is a phytochrome A (phyA)-specific signaling intermediate that acts as a light-dependent repressor of photomorphogenesis in Arabidopsis seedlings. It contains a WD-repeat domain that shows high sequence similarity to the WD-repeat region of the constitutive repressor of light signaling, COP1. Here, using yeast two-hybrid and in vitro interaction assays, we show that SPA1 strongly and selectively binds to COP1. Domain mapping studies indicate that the putative coiled-coil domain of SPA1 is necessary and sufficient for binding to COP1. Conversely, similar deletion analyses of the COP1 protein suggest that SPA1 interacts with the presumed coiled-coil domain of COP1. To further investigate SPA1 function in the phyA signaling pathway, we tested whether SPA1, like COP1, mediates changes in gene expression in response to light. We show that spa1 mutations increase the photoresponsiveness of certain light-regulated genes within 2 h of light treatment. Taken together, the results suggest that SPA1 may function to link the phytochrome A-specific branch of the light signaling pathway to COP1. Hence, our data provide molecular support for the hypothesis that COP1 is a convergence point for upstream signaling pathways dedicated to individual photoreceptors.